Highly Sensitive Detection of Melamine Based on the Fluorescence Resonance Energy Transfer between Conjugated Polymer Nanoparticles and Gold Nanoparticles.

Adding melamine as additives in food products will lead to many diseases and even death. However, the present techniques of melamine detection require time-consuming steps, complicated procedures and expensive analytical apparatus. The fluorescent assay method was facile and highly sensitive. In this work, a fluorescence resonance energy transfer (FRET) system for melamine detection was constructed based on conjugated polymer nanoparticles (CPNs) and gold nanoparticles (AuNPs). The energy transfer efficiency is up to 82.1%, and the system is highly selective and sensitive to melamine detection with a lower detection limit of 1.7 nmol/L. Moreover, the interaction mechanism was explored. The results showed that the fluorescence of CPNs were firstly quenched by AuNPs, and then restored after adding melamine because of reducing FRET between CPNs and AuNPs. Lastly, the proposed method was carried out for melamine detection in powdered infant formula with satisfactory results.

[Immune response of Th17 cells in mesenteric lymph node of mice infected by Schistosoma japonicum].

OBJECTIVE: To observe the immune response of Th17 cells in mesenteric lymph node (MLN) of C57BL/6 mice infected by Schistosoma japonicum. METHODS: Twenty C57BL/6 mice were randomly divided into infected group and control group each with ten mice. The mice in infected group were infected each with 40 +/- 5 S. japonicum cercariae. Five to six weeks later, MLN lymphocytes were separated and stimulated for 4 h by anti-CD3 (1 microg/ml) and anti-CD28 (1 microg/ml) before examination of IL-17 and retinoic acid receptor-related orphan receptor gammat (ROR-gammat) mRNA by reverse transcription PCR. The level of IL-17 and IFN-gamma was detected by ELISA after culturing with supernatant for 72h. MLN lymphocytes were stimulated for 5h by 10 ng/ml phorbol myristoyl acetate (PMA) and 1 microg/ml ionomycin. The intracellular cytokines were stained and the content of Th17 and other cytokines was examined by flow cytometry. RESULTS: The level of IFN-gamma [(214.3 +/- 62.6) pg/ml] and IL-17 [(176.8 +/- 62.1) pg/ml] in the supernatant of cultured MLN cells from the infected mice was significantly higher than that of normal mice [(467 +/- 13.9) and 0 pg/ml) (P < 0.05). The expression level of IL-17 and ROR-gammat mRNA was also considerably higher than that of normal mice. IL-17+ IL-4+, IL-17+ IFN-gamma+, IL-17+ IL-5+ and IL-17+ IL-9 cells accounted for 0.06%, 0.02%, 0.02%, and 0.01% of the mesenteric lymph node CD4+ T cells of the infected mice, respectively. However, IL-17+ IL-10+ and IL-17+ Foxp3+ cells were undetected. CONCLUSION: The MLN of S. japonicum-infected C57BL/6 mice can induce the production of Th17 cells, and these cells can secrete IL-4, less IFN-gamma, IL-5 and IL-9, but not IL-10, and can not express Foxp3 in the infected mice.